松辽盆地嫩江组脱羟基维生素E的分布及其地球化学意义  

The distribution of methylated-2-methyltrimethyltride-cylchromans and geochemical implication in Nenjiang Formation of the Late Cretaceous from Songliao Basin

作　　者：王丽[1,2] 宋之光[1] 

机构地区：[1]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [2]中国科学院研究生院,北京100049

出　　处：《地球化学》2010年第5期469-478,共10页Geochimica

基　　金：国家重点基础研究发展计划项目(2006CB701404)

摘　　要：脱羟基维生素E是沉积物(岩)中一类具有水体盐度指示意义的生物标志化合物,在现代和古代沉积物及原油中均有检出。在松辽盆地松科1井晚白垩系嫩江组岩芯样品中检测发现的脱羟基维生素E系列化合物显示脱羟基维生素E的组成分布在剖面上的变化主要反应了沉积埋葬时的环境盐度、氧化还原状态的变化,而与母源组成、有机质成熟度等无明显相关性;其中,δ-MTTC在咸水还原性环境最为丰富,而在低盐的半咸水-淡水氧化性环境中基本缺失;α-MTTC在所有盐度环境中都很丰富,γ-MTTC的丰度则在盐水-咸水环境中明显高于低盐半咸水环境,而且在盐水环境中γ-MTTC>β-MTTC,咸水环境显示γ-MTTC<β-MTTC。研究发现,α-MTTC/γ-MTTC(α/γ)可作为α-MTTC/δ-MTTC(α/δ)比值的替代指标,当α-MTTC/γ-MTTC比值小于2时为盐水环境,比值大于15时为半咸水-淡水环境,介于之间为咸水环境。相关参数及综合分析显示嫩江组一、二段沉积时期水体盐度及氧化还原条件显著不同,嫩一段主力烃源岩沉积时期以与海水盐度相当的咸水、存在水体分层的还原性湖泊环境为主,顶部出现短期咸化的盐水环境;而嫩二段主要为半咸水-淡水氧化性湖泊环境,盐度比较稳定。Methylated-2-methyltrimethyltride-cylchromans （MTTCs） is a salinity indicating biomarkers that are widely detected in modern and ancient sediments and crude oil. The composition and distribution of methyled-MTTCs identified m Late Cretaceous core samples of Nenjiang Formation （K2n^1 and K2n^2） of SK-1 drilling from Songliao Basin are mainly indicative of the depositional environment of salinity, redox state and their variation on the profile, while bearing no relation with organic matter types, burial depths, maturity. Among these MTTCs, δ-MTTC is abundant in salty reduction environment while absent in the low salinity aerobic environment, while α-MTTC is a non-salinity dependent compound and rich in all environments, while γ-MTTC shows a relatively higher abundance in the higher salinity environment than that of lower saline environment; furthermore, relative abundance of two dimethyl-MTTCs display a relation of γ-MTTC〉β-MTTC in higher-salinity environment, but γ-MTTC〈β-MTTC in lower salinity environment. This study also shows that α-MTTC/γ-MTTC （α/γ） ratio is also indicative of the salinity of water environments, as when the α/γ ratio is less than 2, which indicates a mesosaline environment, when a ratio of greater than 15 is indicative of a senti-saline to freshwater lacustrine environments, while a ratio between 2 and 15 is indicative of normal marine-ike salinity environment. The combination of all related indexes and biomarkers suggests that K2n^1 and K2n^2 were formed under significantly different salinity, as the K2n^1 was likely developed under a normal marine salinity-like environment with a short period of mesosaline environment at the top section; while K2n^2 was likely developed under a semi-saline to freshwater lacustrine environment with a relative stable salinity.

关 键 词：脱羟基维生素E 古盐度 沉积环境 嫩江组 松辽盆地 

分 类 号：P593[天文地球—地球化学]